Harsh pace, and not disheartened (8)
I believe the answer is:
strident
'harsh' is the definition.
(thesaurus)
'pace and not disheartened' is the wordplay.
'pace' becomes 'stride' ('stride' can be a synonym of 'pace'**).
'and' means one lot of letters go next to another.
'disheartened' says to hollow out the word (remove centre letters).
'not' with its centre removed is 'nt'.
'stride'+'nt'='STRIDENT'
(Other definitions for strident that I've seen before include "ear-piercing" , "harsh noise" , "Offensively loud and harsh" , "Loud and harsh over tridents" , "Shrill" .)